sedimentary

Fossil Crab

Decapoda (likely Avitelmessus or Raninidae family)

AI-generated identification · may be incorrect

Hardness: 3-4 (calcite based); Color: Tan, beige, or grey; Luster: Dull or earthy; Crystal structure: Amorphous fossil replacement; Cleavage: None; SG: 2.6-2.8

Hardness: 3-4 (calcite based)
Color: Tan, beige, or grey
Luster: Dull or earthy

Identified April 11, 2026More sedimentary →

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Physical properties

Hardness: 3-4 (calcite based); Color: Tan, beige, or grey; Luster: Dull or earthy; Crystal structure: Amorphous fossil replacement; Cleavage: None; SG: 2.6-2.8

Formation & geological history

Formed through the process of permineralization or replacement within marine sedimentary deposits, often during the Cretaceous or Tertiary periods, as sediment encased organic remains.

Uses & applications

Educational purposes, museum display, and private fossil collecting.

Geological facts

Fossil crabs are often found within concretions—hard, spherical masses of sedimentary rock that form around organic matter. Crabs have been on Earth for over 200 million years.

Field identification & locations

Look for symmetrical carapace structures, segmented legs, or pincers often encased in nodular stones. Common in coastal sedimentary formations or ancient seabed exposures.